Project EUROLIFT Research Articles

Recent research topics in high-lift aerodynamics

High-lift systems are matured, robust and reliable components of a transport aircraft. Although facing nearly 100 years of history, there is an ongoing need of research in the aerodynamics of such systems due to changes in the requirements for aircraft development. Other than in former times, high-lift aerodynamics research is nowadays more incorporated into larger projects. It is, therefore, not as visible as before when dedicated high-lift projects were conducted, as e.g., the EC funded project EUROLIFT. The aim of this summary is to collect from different projects, the current challenging research topics in the area of high-lift aerodynamics. The contribution gives an overview on recent research topics addressed at the German DLR Institute of Aerodynamics and Flow Technology in collaboration with national and international partners.

Advanced Design by Numerical Methods and Wind-Tunnel Verification Within European High-Lift Program

The design activity within the European 6th framework project EUROLIFT II is targeted towards an improvement of the take-off performance of a generic transport aircraft configuration by a redesign of the trailing edge flap. The involved partners applied different optimization strategies as well as different types of flow solvers in order to cover a wide range of possible approaches for aerodynamic design optimization. The optimization results obtained by the different partners have been cross-calculated in order to eliminate solver dependencies and to identify the best obtained design. The final selected design has been applied to the wind tunnel model and the test in the European Transonic Wind Tunnel (ETW) at high Reynolds number confirms the predicted improvements.

Transition Prediction and Impact on a Three-Dimensional High-Lift-Wing Configuration

The evolution of maximum lift coefficient of a transport aircraft as a function of Reynolds number can be linked to modifications of the laminar-turbulent transition process. In the framework of European project EUROLIFT (I), a task was dedicated to the physical understanding and the numerical modeling of the transition process in high-lift configurations. Then, in the follow-on project EUROLIFT II, a major step is the integration of transition prediction tools within Reynolds-averaged Navier-Stokes (RANS) solvers in order to estimate the impact of transition on performance. This paper presents an overview of the different activities dealing with transition in the EUROLIFT II project.

Transition on a High-Lift Swept Wing in the European Project EUROLIFT

Performance of transport aircraft in high-lift conditions is directly related to the maximum lift. However, most of the high-lift tests are carried out at subscale conditions, and performance is then derived by extrapolation to flight Reynolds number. So-called adverse Reynolds number effects (sudden decrease of maximum lift with increasing Reynolds number) often occur when extrapolations from the wind-tunnel and flight-tests results are compared. Most of these effects are due to changes in the transition process. Improvement of the knowledge of the transition process for three-dimensional high-lift configurations is, thus, necessary. Therefore, specific experimental and numerical tasks were decided on within the European research project EUROLIFT, dedicated to high-lift aerodynamics. Within this program, a generic high-lift swept wing was first tested by the use of wall hot films and infrared thermography in the ONERA F1 pressurized wind tunnel to study Reynolds number effects on transition. This test campaign provided a detailed database for the transition prediction tools developers and for the assessment of numerical methods. Based on accurate pressure distributions obtained from three-dimensional Navier‐Stokes computations, a theoretical and numerical study of transition was conducted based on both exact and simplified stability approaches. Results contributed to a better understanding of transition phenomena in high-lift conditions, as well as to extension of the validity of methods and rules used to predict attachment line contamination, relaminarization, and stability-based transition.